Cut up manuscript for tests (5)
I believe the answer is:
exams
'for tests' is the definition.
('exam' can be a synonym of 'test')
'cut up manuscript' is the wordplay.
'cut' becomes 'axe' (both can mean to cancel or remove).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'manuscript' becomes 'ms' (abbreviation for manuscript).
'axe' back-to-front is 'exa'.
'exa'+'ms'='EXAMS'
(Other definitions for exams that I've seen before include "Important tests" , "Tests for students" , "summer term commitment?" , "GCSE, A-level, etc" , "papers" .)